Study shows pollution levels in some kitchens are higher than city centre hotspots

A study by the University of Sheffield has found that the air we breathe inside our own homes can have pollutant levels three times higher than the outdoor environment, in city centres and along busy roads.

Researchers from the University’s Faculty of Engineering measured air quality inside and outside three residential buildings with different types of energy use (gas vs. electric cookers). They found that nitrogen dioxide (NO2) levels in the kitchen of the city centre flat with a gas cooker were three times higher than the concentrations measured outside the property and well above those recommended in UK Indoor Air Quality Guidance1. These findings are published in the Journal of Indoor and Built Environment.

"We spend 90 per cent of our time indoors and work hard to make our homes warm, secure and comfortable, but we rarely think about the pollution we might be breathing in," said Professor Vida Sharifi, who led the research. "Energy is just one source of indoor pollution, but it is a significant one. And as we make our homes more airtight to reduce heating costs, we are likely to be exposed to higher levels of indoor pollution, with potential impacts on our health."

The study, funded by the Engineering and Physical Sciences Research Council (EPSRC INTRAWISE Consortium), compared a rural house with two flats, one in Sheffield city centre and the other in an urban location next to a busy road. The rural house had an electric cooker while both flats used gas appliances. Samples were taken outside and inside the properties, from each kitchen, over a four week period.

The researchers, Professor Sharifi, Professor Jim Swithenbank and Dr Karen Finney, focused on pollutants known to have a detrimental health impact, particularly on the elderly and people with respiratory or cardiovascular problems.

Key facts

Nitrogen dioxide (NO2) levels in the kitchen of the city centre flat with a gas cooker were three times higher than city centre hotspots.

The average particle concentrations measured by the research team in the kitchens of both flats with gas cookers were higher than the levels set by the Government as its objective for outdoor air quality.

These included carbon monoxide (CO), nitrogen dioxide (NO2), volatile organic compounds (VOCs) and solid particles small enough to penetrate into the lungs (2.5 microns in size or smaller, known as PM2.5).

The average particle concentrations measured by the research team in the kitchens of both flats with gas cookers were higher than the levels set by the Government as its objective for outdoor air quality in both London and England2. There are currently no set guidelines for safe levels of particles in the home.

Professor Sharifi said: "Concerns about air quality tend to focus on what we breathe in outdoors, but as we spend most of our time indoors, we need to understand more about air pollution in our homes. There is very little data on emission rates from different appliances or acceptable standards on indoor pollutants.

"Although ours was just a small study, it highlights the need for more research to determine the impact of changing housing and lifestyles on our indoor air quality."

Additional information

1Guidance on the effects on health of indoor air pollutants, December 2004, Committee on the Medical Effects of Air Pollutants, Department of Health Department of Health guidance (p43)

2UK outdoor air quality standard for particles measured as PM10 is 50 μg/m3(24-hour average concentration) and Air Quality Objectives are 23 and 20 μg/m3 (annual average concentration) for London and other locations in England respectively. (COMEAP guidance as above, point 43 on p19)

C. Tan, K.N. Finney, Q. Chen, N.V. Russell, V.N. Sharifi and Swithenbank, J. (2012) Experimental investigation of indoor air pollutants in residential buildings, is published by Indoor and Built Environment.

Professor Vida Sharifi is Head of the Energy and Environmental Engineering Research Group in the University of Sheffield’s Faculty of Engineering and the Director of the Sheffield University Waste Incineration Centre for Research (SUWIC).

The University of Sheffield’s Faculty of Engineering The Faculty of Engineering at the University of Sheffield - the 2011 Times Higher Education’s University of the Year - is one of the largest in the UK. Its seven departments include over 4,000 students and 900 staff and have research-related income worth more than £50M per annum from government, industry and charity sources. The 2008 Research Assessment Exercise (RAE) confirmed that two thirds of the research carried out was either Internationally Excellent or Internationally Leading.

The Faculty of Engineering has a long tradition of working with industry including Rolls-Royce, Network Rail and Siemens. Its industrial successes are exemplified by the award-winning Advanced Manufacturing Research Centre (AMRC) and the new £25 million Nuclear Advanced Manufacturing Research Centre (NAMRC).

The Faculty of Engineering is set to ensure students continue to benefit from world-class labs and teaching space through the provision of the University's new Engineering Graduate School. This brand new building, which will become the centre of the faculty´s postgraduate research and postgraduate teaching activities, will be sited on the corner of Broad Lane and Newcastle Street. It will form the first stage in a 15 year plan to improve and extend the existing estate in a bid to provide students with the best possible facilities while improving their student experience.

The Engineering and Physical Sciences Research Council (EPSRC)The Engineering and Physical Sciences Research Council (EPSRC) is the UK’s main agency for funding research in engineering and physical sciences. EPSRC invests around £800m a year in research and postgraduate training, to help the nation handle the next generation of technological change.

The areas covered range from information technology to structural engineering, and mathematics to materials science. This research forms the basis for future economic development in the UK and improvements for everyone’s health, lifestyle and culture. EPSRC works alongside other Research Councils with responsibility for other areas of research. The Research Councils work collectively on issues of common concern via research Councils UK.